The goal of the work is to conduct a feasibility study on the topic of visual navigation during lunar landing using neuromorphic hardware and software - specifically event cameras and spiking neural networks. These lightweight and low power devices are promising for the next generations of landers. The event camera is simulated during several optimal descents. The results are processed using convolutional spiking neural networks to produce optical flow, which is then turned into vehicle egomotion estimates using continuous homography relations. It is found that a relevant event-based dataset can be created and, to an extent, validated. The chosen spiking neural networks are capable of recognizing the lander motion from the events, but struggle to focus on local detail and to properly generalize as a result. They however, do not far worse than their non-spiking counterparts.

Solar cells have been used on satellites since early after their invention, now present on virtually every satellite. To accommodate the power consumption of satellites, large panels have to be fitted to it. These are normally folded in a harmonica-like way, to fit within the launch vehicle fuselage, and deployed when in orbit. Each solar array features different parameters, defining its deployment behaviour. While limited research has been performed on the behaviour of individual arrays, a lack of research into a generalised response to parameter variations can be observed. The research of this Master's thesis focused on the characterisation of solar array deployments, identifying the influence of array parameters on the deployment, and the differences between test, simulation, and operation environments. Additionally, the test results were used in a correlation study together with the results of a simulation model for validation and investigation of on-Earth effects.

To support the integration of Acousto-Optic Tunable Filters (AOTFs) in optical systems and lay the groundwork for further research, this report presents the development and validation of an analytical model for a noncollinear AOTF based on tellurium dioxide (TeO2). The AOTFs are compact solid-state devices that filter desired optical wavelengths by applying an appropriate RF signal. Their compactness and quick tunability make them particularly appealing for Earth observation missions, where an AOTF can be integrated into small platforms like CubeSats.

However, there is a significant gap in the availability of comprehensive optical AOTF simulations that can predict the behaviour of AOTFs, and specify the momentum-matching frequencies required for the highest diffraction efficiency (DE) to occur. This report addresses that gap by developing a detailed three-dimensional (3D) analytical model for the non-collinear AOTFs based on TeO2, the most commercially available and widely used AOTF configuration. The analytical model, developed in this report, aims to facilitate the design and optimization of AOTFs for optical systems used in various fields, particularly in space-based instruments.

The core of the AOTF’s analytical model can be broken down into three main stages: the entrance facet, the acoustic field, and the exit facet. The interaction of light with these three stages is simulated by rays, the direction of which is determined by the Directional Cosine Matrices (DCMs). The model performs calculations to describe the path of incoming rays as they enter, propagate through, and exit the AOTF crystal. Special attention is given to simulating the Acousto-Optic (AO) interaction within the crystal, where a diffracted light is produced. Furthermore, the model calculates the momentum-matching frequency and outputs the propagation
of a newly created diffracted light through the AO interaction.

The developed model is adapted to operate for both incident polarisation types, ordinary and extraordinary. Furthermore, the model can simulating the AOTF’s behaviour as it is rotated, allowing further versatility of AOTF’s placement in the optical design. The model, as well as the adaptations, were first verified with the data from the Voloshinov et al. paper, where it accurately predicted both the separation angles and the momentum-matching frequencies. Further verification was performed with known AOTF parameters at various optical wavelengths with the help of an experiment performed at Université Polytechnique Hauts-de-France (UPHF).

Furthermore, the model was validated through diffraction testing, where it successfully simulated the AOTF’s behaviour, predicting both diffracted and undiffracted ray angles with an accuracy of 0.1 degrees. Testing was conducted at various rotational angles and for both incident polarisation types, with the model’s predictions closely matching the experimental data. Based on the testing, it was possible to determine the frequency-matching method used in characterising the essential AOTF angles that dictate the AOTF’s behaviour.

The analytical model was further enhanced by incorporating an optimization algorithm, which automates the characterization of key AOTF variables for newly acquired devices. The algorithm characterises the crystallographic axis angle, tilt angle, and facet inclination angles. These parameters are typically not provided by manufacturers, leaving the AOTF’s behaviour largely unknown. However, by characterising these variables with the model created, it becomes possible to extrapolate the AOTF’s performance for any incident optical wavelength within the visible spectrum.

The thermal analysis of small satellites (SmallSats) is often given a low priority compared to other sub-systems, due to the short timelines and small budgets associated with SmallSats. However, the satellite's temperature is crucial for preventing mission failures. In this thesis, a new, open-source, modular software for thermal analysis of SmallSats is created with the Python coding language, to simplify and speed up the thermal analysis process. This modularity is achieved by: ensuring that any thermal model can be connected to any other thermal model with a single connect function, allowing a hierarchical model structure that is easily mutable and re-usable; integrating a material database into the software, allowing frequent re-use of common materials, coatings, and contact connections; and including a dedicated sensitivity analysis tool in the software to allow the user to assess the sensitivity of the model's temperatures on various input parameters. To assess the quality of the software's computations, they were verified with the commercial ESATAN-TMS software, and validated with flight data from the FUNcube-1 CubeSat. The validation showed Root-Mean-Square Errors ranging from 1.4 degrees C to 7.1 degrees C for the outside panels of the satellite. With a sensitivity analysis performed on FUNcube-1, it was found that the solar absorptivity of the spacecraft demonstrates the greatest influence on simulation outputs: the largest risk may be its degradation throughout time, due to ultra-violet and atomic oxygen exposure. If the satellite would have had white paint, a year-long degradation could lead to a 17.1 degrees C temperature increase of the maximum achieved temperature in the satellite, depending on the type of paint used. Further development into this software should aim to validate the model even further with different satellites, which will be an important step towards making this tool a standard for SmallSat thermal analysis.

This thesis work proposes an approach to integrate design and reliability assessment, based on a single modeling environment by deployment of Systems Modeling Language (SysML). The main purpose of the developed approach is to help enhance reliability assessment in student-based CubeSat projects. Considering the limited project resources, that CubeSat university design teams typically have to cope with, an attempt is made to create a methodology, that allows adoption of single modeling environment for both system design and reliability analysis, thereby focusing on the main principles and advantages offered by the Model-Based Systems Engineering (MBSE) practice. To develop the considered methodology and to demonstrate its practical application the following steps were taken: A SysML design model is built, consisting of both functional and physical architectures, based on a hypothetical simplified spacecraft subsystem. Thereby an assessment is made to what detail a system needs to be modeled and which characteristics it should at least comprise to provide a sufficient basis for a risk model, as a choice of a certain risk assessment methodology may influence the extent to which a system must be modeled, while certain system design model characteristics influence the selection of the appropriate risk assessment methods to be implemented. To determine how risk analysis can be performed in SysML for a given hypothetical design problem, various risk assessment methods were considered for the sake of risk assessment methodology development, based on specific criteria. After it became clear how the implementation of both qualitative and quantitative parts of risk assessment had to be realized in SysML, the actual risk analysis was initiated; the design model was extended by a reliability model. The evaluation on the obtained results was finally performed, and general observations from integrating risk analysis in MBSE were presented, based on the comparison with traditional methods, considering the major risk assessment aspects.

CryoSat-2 is a European Space Agency (ESA) altimeter mission with an objective to study the connection between cryosphere melting and global sea level rise. The satellite carries a Doppler navigation system (DORIS) and a Satellite Laser Ranging system (SLR) to aid the precise computation of orbits down to centimetre level.
CNES/IDS releases DORIS tracking data in two formats for CryoSat-2. One is the raw format called RINEX and other is the pre-processed Doppler format called version 2.2. V2.2 data contains all information necessary for straightforward usage in orbit determination - measurements time-tagged in TAI, range-rate measurements, ionospheric correction, tropospheric correction, antenna corrections and flags that indicate unusable measurements. RINEX does not contain any corrections and has the phase and pseudorange measurements at short latency allowing users to have flexibility in processing. Additionally, data required for formulating the corrections are present in RINEX. For missions in and after 2016, CNES/IDS supplies tracking data only in RINEX and not in V2.2. Analysis centres using DORIS data now have to independently develop processing strategies to process RINEX data. This problem is the main objective of this research. In this thesis, a pre-processor called RX2RR (RINEX to Range-Rate) has been built in Fortran in an attempt to process the raw data and compute all the necessary corrections. RX2RR converts RINEX format to a format exactly similar to V2.2 such that RINEX can now be used in any orbit determination tool that has been previously using V2.2. In this processor, clock synchronisation of on-board clock to International Atomic Time is performed. A new approach of utilizing Meteorological data in RINEX for troposphere delay corrections is implemented. Use of real time data from numerical weather models is also presented for tropospheric correction. Ionospheric delay and antenna phase centre corrections are performed using iono-free phase centre. An editing strategy to remove outliers in Doppler data is implemented and tested. To demonstrate the performance of the tool, we perform orbit determination using NASA Goddard Space Flight Center’s orbit computation software GEODYN-II. We use RX2RR processed RINEX data and CNES processed V2.2 data of CryoSat-2 for year 2016. Tracking residuals from both POD runs are compared and average difference in R.M.S residual is found to be approximately 0.011 mm/s over a year. This validates that the corrections are formulated and implemented correctly. The result proves our capability to process the RINEX measurements independently and the tool developed has extended the capability of GEODYN-II to process RINEX observations from DORIS system.

Measurements in the frequency range below 30 MHz, key to a better understanding of the origins of our universe, are one of the last unexplored areas of radio astronomy. Low frequency measurements suffer greatly from disturbance from man-made signals. Therefore, satellite missions are proposed which use the Moon as a shield from these disturbances, by making use of the Earth-Moon L2 Lagrange point. Such missions require large numbers of small satellites. One of the challenges for these missions is getting the satellites into their destination orbit with a very small Delta V budget. This research looks into the use of low energy trajectories for such a mission transfer trajectory.
Low energy trajectories are found on the invariant manifolds of the CR3BP and may be classified into several categories. Different combinations of these categories lead to different types of transfer trajectories. Four possible combinations were considered in this research, and compared to see which one best suits a small satellite mission to the Earth-Moon L2 Lagrange point. One combination has been previously researched in literature, the other three are new options for a transfer to the Earth-Moon L2.
The approach known from literature resulted in transfers with a required Delta V of down to 28 m/s. Using one of the other approaches, this could be reduced to 9 m/s. Additionally, one of the approaches allows for a station-keeping orbit around the Sun-Earth L2 point, which does not only make scheduling of the transfer easier, but also allows for additional mission objectives. These are encouraging results, showing that possibilities exist for the use of low energy trajectories for a lunar L2 mission.